Tephrostratigraphy of the Pliocene Ikego Formation on the northern Miura Peninsula and correlation with widespread tephra beds in central Japan

The Ikego Formation is one of the upper Pliocene stratotype sections of the northwestern Pacific region, owing to the abundant tephra beds in the formation and a robust chronological framework based on biostratigraphy and magnetostratigraphy.This study aimed to correlate tephra beds in the Ikego Formation with widespread tephra beds in other basins in central Japan, based on microscopic observations, heavy mineral compositions, and refractive index measurements and elemental analyses of glass shards from 10 vitric fine ash tephra beds (IkT03, IkT16, IkT19, IkT28, IkT34, IkT37, IkT41, IkT45, IkT63, and IkT75).As a result, IkT45 is correlated with Msg-Iwm of the Kobiwako and Tokai groups, and IkT75 is correlated with Hbt1-MT2, which is widely recognized in other Pliocene basins in central Japan.